Yan Bixing, Wan Dongyang, Chi Xiao, Li Changjian, Motapothula Mallikarjuna Rao, Hooda Sonu, Yang Ping, Huang Zhen, Zeng Shengwei, Ramesh Akash Gadekar, Pennycook Stephen John, Rusydi Andrivo, Martin Jens, Venkatesan Thirumalai
NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore.
Singapore Synchrotron Light Source , National University of Singapore , Singapore 117603 , Singapore.
ACS Appl Mater Interfaces. 2018 Nov 7;10(44):38201-38208. doi: 10.1021/acsami.8b11643. Epub 2018 Oct 26.
Large polarons have been of significant recent technological interest as they screen and protect electrons from point-scattering centers. Anatase TiO is a model system for studying large polarons as they can be studied systematically over a wide range of temperature and carrier density. The electronic and magneto transport properties of reduced anatase TiO epitaxial thin films are analyzed considering various polaronic effects. Unexpectedly, with increasing carrier concentration, the mobility increases, which rarely happens in common metallic systems. We find that the screening of the electron-phonon (e-ph) coupling by excess carriers is necessary to explain this unusual dependence. We also find that the magnetoresistance could be decomposed into a linear and a quadratic component, separately characterizing the carrier transport and trapping as a function of temperature, respectively. The various transport behaviors could be organized into a single phase diagram, which clarifies the evolution of large polaron in this material.
大极化子近来在技术领域备受关注，因为它们能够屏蔽并保护电子免受点散射中心的影响。锐钛矿型TiO₂是研究大极化子的一个模型体系，因为可以在很宽的温度和载流子密度范围内对其进行系统研究。考虑到各种极化子效应，对还原态锐钛矿型TiO₂外延薄膜的电子和磁输运性质进行了分析。出乎意料的是，随着载流子浓度的增加，迁移率反而增大，这种情况在普通金属体系中很少发生。我们发现，过量载流子对电子 - 声子（e-ph）耦合的屏蔽作用对于解释这种异常的依赖关系是必要的。我们还发现，磁电阻可以分解为线性和二次分量，分别表征载流子输运和作为温度函数的俘获情况。各种输运行为可以整理成一个单相图，这阐明了该材料中大极化子的演化过程。
